October 26, 2009
Blue Light-Filtering Increases Macular Pigment, May Protect Against Age-Related Vision Loss
Age-related macular degeneration, a major cause of vision loss, affects millions of older persons
Results of an important new study show that implantation of blue light-filtering intraocular lens (IOLs) at the time of cataract surgery increases a nutritional component of the eye, which may afford protection against the development and/or progression of age-related macular degeneration (AMD). The study, conducted by leading ophthalmology and vision researchers from the Macular Pigment Research Group at the Waterford Institute of Technology, is published in the October 2009 issue of the high impact journal Investigative Ophthalmology & Visual Science (IOVS).
AMD is a disease affecting the central part of the retina and is the leading cause of vision loss in the developed world. Implantation of lenses that do not filter blue light during cataract surgery has been shown to increase the risk for development and/or progression of AMD.
"Blue light-filtering lenses filter and block damaging blue light from reaching the retina, which holds the potential of reducing vision loss and improving the quality of life for millions of older patients," said the study's chief investigator, John M. Nolan, Fulbright Scholar, BSc, PhD, deputy director, Macular Pigment Research Group, Waterford Institute of Technology, Waterford, Ireland. "These data represent an important first step in fully realizing the benefits of blue light-filtering in improving a nutritional component of the eye known as macular pigment. There is a strong scientific rationale supported by an ever-growing body of scientific evidence which suggests that macular pigment plays a role in reducing the onset and progression of AMD."
Dr. Nolan and fellow Macular Pigment Research Group researchers discovered an increase in macular pigment levels shortly after cataract surgery among the study patients who had blue light-filtering IOLs implanted.
"Since prolonged exposure to blue light is harmful to the retina, increased levels of macular pigment are considered a strong surrogate marker for protection against the processes that cause age-related blindness, including AMD," says Dr. Nolan.
According to the study, the potential benefits associated with increased macular pigment resulting from the use of blue light-filtering lenses for prevention and/or decreased progression of AMD would be conferred at the time of cataract surgery and are expected to continue thereafter, over a patient's lifetime. This is especially meaningful in the modern era of cataract surgery, which is being performed annually in millions of older persons who live for many years after the procedure, as well as certain patient subgroups, who have had the surgery at an earlier age. The researchers note that further studies are needed to confirm the clinical benefit of their findings.
About the Study
Dr. Nolan and colleagues conducted a prospective study in which 42 patients scheduled for cataract surgery were randomized to implantation with a blue light-filtering acrylic IOL or a standard acrylic IOL (control), with macular pigment optical density measured by a reliable method (heterochromatic flicker photometry), and serum concentrations of the macular carotenoids were quantified by a scientific procedure known as high performance liquid chromatography, prior to surgery and then at several post-procedural time points over a 1-year follow-up period.
Cataract surgery in older persons, where the natural diseased lens (cataract) is replaced with a clear artificial IOL, has been associated with increased subsequent risk for macular disease, perhaps due to increased transmission of potentially injurious short-wavelength (blue) light to the retina.
Therefore, lens manufacturers have incorporated a blue light-filter into IOLs to help reduce photo-oxidative retinal injury and thereby reduce the risk of new-onset AMD and/or its progression. Evidence suggests that photo-oxidative stress is important in the development of AMD. The likelihood of retinal damage is highest for short-wavelength light (blue light). Several parts of the eye, most importantly the lens, act as filters to block short-wavelength light from reaching the retina.
Macular pigment is thought to protect against AMD because it absorbs short-wavelength (blue) light before it reaches photoreceptors in the retina and because of its antioxidant properties (decreases oxidative stress by quenching free radicals). Portions of the eye behind (posterior to) macular pigment are exposed to approximately six times the amount of blue light in persons having the lowest levels of macular pigment, as compared to those with the highest levels. Macular pigment is obtained entirely from the diet and transported to the retina via the blood. Therefore, ongoing research is being conducted to determine to what extent a person's diet may affect AMD. However, the data available to date is in support of such a notion.
About Cataracts and AMD
As the aging population grows and becomes a larger percentage of the overall population, age-related diseases such as cataracts and AMD will become more prevalent.
Surgical removal of cataracts "“ lens that have become clouded from buildup of protein "“ is the most frequently performed surgery in the U.S.7, with more than 6 million cataract surgeries currently performed each year in the U.S. and Europe combined. While vision is almost universally improved immediately following cataract removal, implantation of lens that does not filter harmful short wavelength (blue) light may hasten the progression of AMD, the leading cause of vision loss in people over the age of 60 in the U.S.
AMD is a disease that affects part of the back of the eye called the macula, the central part of the retina. The central vision of affected individuals becomes blurry or wavy and can be eventually lost, which severely alters their quality of life. Approximately 25-30 million individuals are affected worldwide, with the number estimated to triple in the next 25 years.
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